The index went up 3.37 points or 0.24 per cent to 1,424.31 points, on turnover of Bt20.88 billion. Turnover in the morning session was only Bt8.78 billion.
Asia Plus Securities said in a research note that political concerns would keep the index in the range of 1,400-1,450 points until next week.
"The thin turnover of Bt8.8 billion indicated extremely low confidence and extreme fears to political condition. The market is entirely influenced by politics: for example, the index tested 1,519 points before July 24, only to have lost over 100 points when it was agreed that Pheu Thai's amnesty bill would be the first bill for parliamentary vetting. During July 24-to August 5, the market has lost 6.2 per cent, the most in the region," it said in the note, released in the afternoon.
In the same period, the Philippines lost 3.1 per cent, Japan 2.9 per cent and Indonesia 2.7 per cent.
Foreign investors and Thai individual investors were net-sellers yesterday.
The turnover today was just half of the average daily turnover in July, worth Bt44.4 billion, according to the exchange's data. By month, July's average daily turnover is the lowest in this year, against the peak of Bt68.46 billion in March.